Reception system



R. c. CURTIS 2,071,733

RECEPTION SYSTEM Original Filed June 12, 1934 5 Sheets-Sheet l Feb. 23,1937.

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RECEPTION SYSTEM Original Filed June 12, 1934 3 Sheets-Sheet 3 x L mo80- Q "g; v// ffi:

12o I I I 140 I I FREQUENCY IN KILDCYCLES Richard II. Buriis.

Patented Feb. 23, 1937 UNITED STATES PATENT Y OFFI. ,C.E

RECEPTION SYSTEM tion of Delaware Richard 0. Curtis, East Orange, N.,J.,.assignor to Wired Radio, Inc... New York, N. Y., a corpora-Original application June 12, 1934, Serial No. Y I 2 730,211. Dividedand this application January 9, 1935, Serial No. 94,8 v

1 Claim. (orzso- -zo) i My invention pertains in. general to radioreceiving systems and specifically relates to a universal receiver forreceiving programs under varying conditions, this being a divisional ofmy application Serial No. 730,211, filed June 12, 1934.

One of the objects of my invention consists in providing a radioreceiving system having means for effecting the reception of signalsfrom differently characterized sources.

Another object comprises providing a receiving system, having means forimproving the quality of reproduction by having a plural resonanceaccentuation of the response at certain frequencies.

A further object comprises providing a filter system of the inductivelycoupled type in which variation of frequency band width can beaccomplished without the aid of switches or like devices.

A further object consists in providing a receiving system in which acharacteristic frequency reception curve having staggered or an oddnumber of resonance peaks is varied in width by commonly mechanicallymoved electrical units having no conductive electrical connection withthe other circuits in the system.

These and other objects will be apparent from the following, referencebeing had to the accompanying drawings in which like reference numeralsdesignate corresponding parts throughout and in which:

Fig. 1 is a schematic representation of the circuit system employed inmy invention;

Fig. 2 is a representation of one embodiment of the mechanical structureemployed in part of my receiving system;

Fig. 3 is a horizontal sectional view along the line 3-3 of Fig. 2;

Fig. 4 is a horizontal sectional view along the I line 4-4 of Fig. 2;and

Fig. 5 is a graphical representation of certain characteristics of thereceiving system according to my invention.

My invention contemplates providing a radio receiving system, preferablyof the superheterodyne type, in which the input and output of theintermediate frequency amplifier includes filter networks of theinductively coupled type. Within each filter, according to my invention,there is provided a circuit unit including the primary of one radiofrequency transformer and the secondary of another radio frequencytransformer. The

primary and secondary are interconnected to have special resonancecharacteristics and are also specially mechanically mounted so that theprimary and secondary coils can be moved relative to their associatedwindings to vary coupling effects. and thereby accomplish variations inthe i overall frequency transmission band offreque'ncies beinghandled'by' the intermeditmteirequency amplifier. The transmissioncharacteristics of these filters are such thatthey simulatethe effect ofan odd number of resonance circuits staggered with respectto each otheralongzthe frequency spectrum. Although various odd numbersof suchresonance peaks may be employed according to my invention, I prefer, inthe presentembodiment, to illustrate theme of a system characterized bythree such peaks. z

Referring to' the drawings .in' detail, and particularly to Fig. 1, themixeri :isconnected with circuit means usuallyto .be found in asuperheterodyne receiver ahead. of theintermediate frequency amplifienThis circuit means. connected with the mixer I includes a high frequencyamplifier and high frequency reception circuits as well as the localoscillator for producing oscillations to beat with the received highfrequencies to produce the intermediate frequencies for reception overthe intermediate frequency amplifier. The output of the mixer l isdirected to an input filter circuit 2 which is of the inductivelycoupled type and includes an inductance 3 coupled with inductance 4 andinductance.. ,5 coupled with in.-

ductance 6. Avariable capacitor 1 is incircuit with the inductance 3while a variable capacitor .8

forms; part of the circuit connections betweeninductances 4 and 5.1,Anothervariable capacitor!) is connected'in circuit withwthe.inductance 6. These capacitors are'of the'trimmer type usually to befound in such organizations. The inductance 6 forms part'of the filteroutput circuit which includes aterminating impedance l0 and is connectedwith the input of the intermediate frequencyamplifier proper whichincludes an electron amplifier tube l2. The output of electron amplifiertube i2 is connected, with the input of the output filter circuit whichis similar to the input filter circuit 2. The output of this filtercircuit l I is then connected with the usual detector and audioamplifiersystem'i l and thence to a reproducing loud speaker It. A powersupply I1 is provided in the usual manner for energizing the variouselectron tubes aswell as the loud speaker l5.

Referring to Fig. 2, the mechanical structure of a portion of thereceiving system will now be considered. The inductances 3 and B aremounted'on supporting members 22 and 23 which are secured to a mountingmember 24. A shielding element '21 extends between the coils-3 and 6 asshown.

Cells 3 and 6 are positioned for inductive coupling The entiremechanical structure thus described is mounted within an enclosingshield 30. The shaft 29 extends through the mounting member 24 and ismechanically integral with a crank 3| which is connected with areciprocative member 32 so that reciprocative forces from member 32 canbe translated into rotary motion of 1 the shaft 29. Such rotary motioncauses the'spatial relationship between the coils 3 and 4 and betweenthe coils 6 and to be varied, thus varying the inductive couplingbetween these coils. 'This' condition may be seen particularly in Fig. 3in which the coils have been so rotated.

Referring back to Fig. 1, it will be seen that the reciprocative member32 is provided'for interconnecting the rotatable shafts 29 and 29a inthe two filter systems on the input and output sides of the intermediatefrequency amplifier tube. By such an arrangement, it is possible to varythe coupling in both filter systems in unison. Any convenient form ofknob or dial can be utilized for. controlling the movement of theshaft32 in the structural arrangement of theradio receiver.

Referring to Fig. 5, consideration will now be given to the electricalcharacteristics of the radio receiver of my invention. The curves X, Y,and Z are a family showing the transmission frequency characteristic ofmy radio receiving system for different degrees of coupling produced bydifferent rotative spatial relationship of the coils 4 and 5 in thefilter 2 and filter H. Referring first to curve Z, it will be seen fromthe curve that the frequency band width here is quite wide, while thefrequency band width of curve X is relatively narrow, the curve Y beingintermediate such widths. The curve Z represents close spatialrelationship of the inductance while the curve X represents theopposite. Thus, when it is desired to receive a narrow band offrequencies for program reception purposes, the shaft 32 may be moved tovary the spatial relationship of the coils 4 and 5 with respect to theirassociated coils so that the frequency transmission of the filterassumes a characteristic such as represented by the curve X. On theother hand, to obtain a wider band of frequencies, the spatialrelationship of the coils may be adjusted to obtain a characteristicrepresented by the curve Z. It is an especial feature that themechanical structure of my invention makes it possible to maintain thefilter circuits as a structural unity with the variable means enclosedas a single moving unit Without any physical or conductive connectionwith the rest of the filter circuit, thus avoiding the use of movablecontactors and inductance taps and the like.

It will be seen that the curve Z has substantially three resonance peaksat the points Za, Zb and Zc, while the other curves X and Y have similarresonance peaks but not quite so pronounced, due to the narrower widthof these bands. It is known in the art that filter circuits can beadjusted to achieve certain resonance characteristics and in accordancewith my invention the filter circuits in my system are adjusted toproduce the resonance characteristics indicated in Fig. 5. It will ofcourse be understood that other types of circuits can be employed usingother arrangements of other networks. For example, I might employ a longseries of coupled circuits as Well as other forms of networks. I havefound that such an arrangement of resonance peaks offers considerableimprovement in quality. The attenuation of the side bands correspondingto modulation frequency at around 2300 to 3000 cycles tends tocompensate for the increase in response which is usually present in loudspeakers at these frequencies. The speaker [5 has such a resonancecharacteristic. Another feature is that the carrier is not attenuatedwith respect to the side band frequencies and so does not tend toproduce distortion in demodulation at high precentages V of modulation.

For certain purposes, in accordance with the principles of my invention,the terminating impedances I0 and Mia of the filter systems 2 and I Imay be adjusted in mechanical unison with the adjustment of the spatialrelationship of the inductance coils in these filter systems asaccomplished by the member 32. The relative amplitude of the resonancepeaks is a function of the terminating impedances. In accordance with myinvention, therefore, the values of the terminating impedance for eachfilter system may be made variable so that a strict proportionality Ican be maintained between the reactance values in each filter circuitand the respective value of terminating impedance. It should also benoted that the three resonance peaks may be made to vanish by using asuitably low value of terminating impedance.

It will now be apparent that I have provided a novel form of receivingorganization which is directed to both improvements in electricalreception characteristics and in mechanical arrangements for producingvariable band effects in selection operation. Although I have shown apreferred embodiment of my system it will be apparent that changes canbe made therein by those skilled in the art without departing from theintended scope of my invention. I do not, therefore, desire to limitmyself to the foregoing except insofar as may be pointed out in theappended claim.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

A radio receiving organization comprising, operativeiy associated, aninput super-audible frequency system and intermediary super-audiblefrequency system, a detection and audible frequency amplificationsystem, a loud speaker with a reproducing characteristic accentuated atcertain frequencies, said intermediary super-audible frequency systemincluding an electron am-' plifier tube having input and output circuitsand coupling means having a frequency responsive characteristic havingattenuation to restrict the intermediary super-audible frequenciespositioned in that part of the frequency spectrum which will compensatefor said accentuated audible frequencies of said loud speaker andcomprising two link circuits respectively coupling the input circuit andoutput circuit of said electron amplifier tube with said radio receivingorganization solely by induction and being otherwise conductivelyisolated from said radio re ceiving organization and means for varyingthe physical relation of said inductive couplings of position to effectcompensation for said audible frequency accentuation of said loudspeaker to produce substantially uniform reproduction of the audiblefrequencies derived from said detection and audible frequencyamplification system. 5

RICHARD C. CURTIS.

